POSTNATAL DEVELOPMENT OF THE OSSIFICATION CENTERS IN THE BONES OF RAT SKELETON
Ashraf S. Hegab and Reda A. Abdelhamid
Department of Anatomy, Faculty of Medicine, Zagazig University
The ossification centers in most of the bones of the skeleton of the rat appear to be developed by the 3rd day after birth. Most of the skull flat bones were ossified except few areas of the basi-sphenoid and the vomer bones. The maxillary bone was mostly ossified except its lateral wall that separated it from the maxillary sinus that still cartilaginous. The mandible was completely ossified without evidence of teeth eruption. The thoracic vertebrae showed partial ossification of the pedicles and lamina and most of their bodies while the coccygeal segments still cartilaginous. In the limb bones, the mid-shaft of humerus and femur were ossified. The first phalanx of third digit of fore-limb showed center of ossification, while all first phalanges of hind-limb digits were ossified, other phalanges of both limbs were still cartilaginous. In the regions of complete ossification a lot of histocytes were present that may play role in helping ossification by cleaning the site of ossification. Moreover, there were numerous osteoclasts in the region of femoral growth plate cartilage and other ossification centers.